FIELD OF THE INVENTION
This invention relates to the hydrochlorination of vinyltrichlorosilane in the presence of a catalyst. More particularly, this invention relates to the virtually quantitative preparation of .beta.-chloroethyltrichlorosilane by hydrochlorination of vinyltrichlorosilane in the presence of a Lewis catalyst at 30.degree. to 65.degree. C at about normal pressure.
It is known that .beta.-chloroethyltrichlorosilane forms in the reaction of vinyltrichlorosilane with hydrochloric acid. Even when Lewis acids are used as catalysts, an equilibrium is established at reaction temperatures between 120.degree. and 150.degree. C, and accordingly nothing but low yields of chloroethyltrichlorosilane are obtained. The maximum yields amount to about 47 percent. In addition, appreciable amounts of silicon tetrachloride and .alpha.-chlorovinyltrichlorosilane are formed (Ind. & Eng. Chem. 45 (1953), pp. 367-374).
Attempts have been made to shift this equilibrium reaction more towards the .beta.-chloroethyltrichlorosilane by performing this reaction between 0.degree. C and 60.degree. C with the application of pressure. On the basis of Le Chatelier's principle it has thus been possible to increase the yield to a maximum of 95 percent. See German "Offenlegungsschrift" No. 2,242,773.
Accordingly, it has become desirable to provide a process which will yield higher quantities of chloroethyltrichlorosilane than the 47 percent obtained according to prior art processes. More particularly, it has become desirable to provide a process for the preparation of .beta.-chloroethyltrichlorosilane by a simple process wherein the .beta.-chloroethyltrichlorosilane is obtainable in virtually quantitative yields. More especially, it has become desirable to provide such a process using readily available reactants such as vinyltrichlorosilane and hydrochloric acid.